The present invention relates to data transfer for writing data and read data between a host computer and an optical disk device or the like, and more particularly, to data transfer devices in the host computer and the optical disk device or the like. The invention also relates to a data transfer system performing data transfer between these devices, and data transfer methods.
Conventionally, IDE bus (ATA/ATAPI interface standard) has frequently been used for connecting between the main unit of a personal computer, which serves as a host computer, and peripheral devices, such as optical disk devices or the like, for example, a DVD-ROM drive and a CD-R/RW drive, and Ultra DMA has been used for the protocol. In the standard of the Ultra DMA, previously-known transfer modes 0 to 2 have been enhanced to transfer modes 3 and 4, enabling data to be transferred at a transfer rate of 16.77 to 66.7 Mbytes/sec. The standards for transfer modes 5 and 6 (100, 133 Mbytes/sec) are also under development.
The above-described transfer modes have upward compatibility, and the device with a higher transfer mode can select a plurality of transfer rates so that when a partner device has a lower transfer mode, the device with the higher transfer mode can perform transfer at the highest possible rate that the partner device can manage. In other words, the transfer rate between two devices is uniquely decided according to the transfer modes of the two devices.
Generally, when a data transfer rate is higher, data corruption is more likely to occur because of subtle mismatching in bus timing or the like. Even when this happens, it is possible to perform the data transfer successfully by repeatedly transfer the same data; however, the effective data transfer rate decreases according to the number of times the data transfer is repeated.
As mentioned above, in conventional data transfer devices, the data transfer rate between transfer devices is uniquely selected according to the transfer modes of the transfer devices, but the possibility of data corruption is not taken into consideration. It has been found that the selected transfer rate, therefore, does not necessarily produce the optimum effective data transfer rate.
More specifically, according to a trial carried out by the present inventors, data corruption occurred relatively frequently in, for example, a personal computer having a CD-R/RW drive and a DVD-ROM drive connected thereto, when the DVD-ROM drive read out data and transferred them to the personal computer while the CD-R/RW drive was performing a writing operation into a storage medium from the buffer therein in which data have been transferred. When measuring the effective data transfer rate, it was revealed that the transfer rate was sometimes reduced to a transfer rate that is one step slower. It has been common that the data corruption as described above is dealt with by improvement in transfer lines, setting of signal processing timing, or the like. For this reason, decreases in effective data transfer rates have not been perceived as a problem.